Question

我的作业要求我编写一个读取文本文件的程序，然后使用Ceasar密码版本输出该文件的修改版本，该密码根据移位量移动用户调用的文件的字符他们输入。例如，如果我的文件显示为“hi”并且它们将其移动1，那么它应该显示为“ij”。但是当我运行程序时，它无法识别我何时调用in1或out1并且我只是收到错误消息。任何人都可以帮我弄清楚我做错了什么或提出任何关于如何前进的建议？提前谢谢！

#include <iostream>
#include <iomanip>
#include <fstream>
#include <cctype>
using namespace std;

int main()
{
    //Declare user variables
    int shift, file1chars = 0;
    char filename[25];
    ifstream in1;
    ofstream out1;

    do
    {
        in1.clear(); //clear status flags

        //Prompt user to enter name of input file and amount of shift
        cout << "Please enter the name of the input file." << endl;
        cout << "Filename: ";
        cin >> filename;

        //Open file name
        in1.open(filename);

        //Error message if no file
        if (!in1)
            cout << "That is not a valid file. Try again\n";

    } while (!in1);

    do
    {
        out1.clear(); //clear status flags
        //prompt user to input out file     
        cout << "Please enter the name of the output file." << endl;
        cout << "Filename: ";
        cin >> filename;

        out1.open(filename);
        //Error message if no file
        if (!out1)
            cout << "That is not a valid file. Try again\n";
    } while (!out1);

    //write some code to the input file 
    in1 >> "hi"

    //write the integers in a different order to the output file
    out1 << //idk where to go from here to initiate shift 

    //prompt user to enter shift
            cout << "Please intput the shift amount: ";
    cin >> shift;
    cout << "Processing complete" << endl;

    //Call file (?)

    //Tell user file input is complete and is now printing statistics
    cout << "\nShifted input file Complete. Now printing statistics " << endl;

    //Show statistics for file
    cout << "\nStatistics for file: " << filename << endl;
    cout << "------------------------------------------------";

    //Show characters in file and stats before shift
    cout << "\n\nTotal # of characters in file: " << file1chars << endl;
    cout << "Statistics before shift: " << endl;

    //Show file before shift

    //Show user stats after shift
    cout << "\nStatistics after shift: " << endl;

    //File after shift

    //Close files
    out1.close();
    in1.close();
    return 0;
}

Answer 1

我要求您考虑您的要求并编写尽可能接近表达意图的代码，而不是逐行查看您的代码以查看问题的位置。创建遵循预期功能的功能。

获取输入文件名。
获取输出文件名。
阅读输入文件的内容。
转换输入文件的内容以创建输出字符串。
将输出字符串写入输出文件。

在伪代码中，

int main()
{
    infile = get_input_filename()
    outfile = get_output_filename()
    contents = get_file_contents(infile)
    output = transform_input(contents)
    write_output(outfile, output)
}

将其转换为C ++代码：

// Declare the functions.

std::string get_input_filename();
std::string get_output_filename();
std::string get_file_contents(std::string const& infile)
std::string transform_input(std::string const& contents)j
void write_output(std::string const& outfile, std::string const& output);

// Use them in main.

int main()
{
    std::string infile = get_input_filename();
    std::string outfile = get_output_filename();
    std::string contents = get_file_contents(infile);
    std::string output = transform_input(contents);
    write_output(outfile, output);
}

// Implement the functions.

std::string get_input_filename()
{
    std::string filename;
    cout << "Please enter the name of the input file." << endl;
    cout << "Filename: ";
    cin >> filename;
    return filename;
}

std::string get_output_filename()
{
    std::string filename;
    cout << "Please enter the name of the output file." << endl;
    cout << "Filename: ";
    cin >> filename;
    return filename;
}

std::string get_file_contents(std::string const& infile)
{
   std::ifstream inf(infile);
   std::string contents;
   int c;
   while ( (c = inf.get()) != EOF )
   {
      contents += c;
   }
   return contents;
}

std::string transform_input(std::string const& contents)
{
   std::string res;
   // Do the needful to transform contents to res.
   return res;
}

void write_output(std::string const& outfile, std::string const& output)
{
   std::ofstream outf(outfile);
   outf.write(output.c_str(), output.size();
}

Answer 2

如果你能够使用类或结构和函数，我会建议这样的事情：

<强>的main.cpp

#include <string>
#include <iostream>
#include <fstream>
#include "CaesarShift.h"

int main() {
    std::string filename;
    std::cout << "Please enter the name of the input file. ";
    std::cin >> filename;

    std::ifstream fileIn;
    std::string   text;

    fileIn.open( filename );
    if ( !fileIn.is_open() ) {
        std::cout << "Failed to open file: " << filename << "." << std::endl;
    }

    fileIn >> text;
    fileIn.close();

    CaesarText caesarText;
    caesarText.addText( text );    

    std::cout << "Contents of the Caesar Text before peforming a Caesar Shift:\n"
        << caesarText << std::endl;

    int amount = 0;
    std::cout << "Please enter the amount to shift the text ";
    std::cin >> amount;
    std::cout << "Now performing the Caesar Shift: " << std::endl;

    caesarShift( caesarText, amount );

    std::cout << "Caesar Text after performing a Caesar Shift:\n"
        << ceasarText << std::endl;

    std::ofstream fileOut;
    fileOut.open( std::string( "shifted_" + filename ) );
    if ( !fileOut.is_open() ) {
        std::cout << "Failed to open shifted_" << filename << std::endl;
    }
    // Uncomment to print original text to file otherwise only modified text will be printed.
    // fileOut << caesarText.originalText() << std::endl;
    fileOut << caesarText.shiftedText() << std::endl;
    fileOut.close();

    system( "PAUSE" );
    return 0;
}

<强> CaesarShift.h

#ifndef CAESAR_SHIFT_H
#define CAESAR_SHIFT_H  

class CaesarText {
    std::string _originalText;
    std::string _shiftedText;

public:
    caesarText() = default;
    explicit CeasarText( const std::string& text ) :
        _originalText( text ) {}

    void addText( const std::string& text ) {
        _originalText = text;
    }

    std::string originalText() const {
        return _originalText;
    }

    std::string shiftedText() const {
        return _shiftedText;
    }

    friend void caesarShift( caesarText& c, int amount );    
    friend std::ostream& operator<<( std::ostream& out, const caesarText& ceasarText );
};

#endif // !CAESAR_SHIFT_H

<强> CaesarShift.cpp

#include "CaesarShift.h"

#include <string>
#include <iostream>
#include <algorithm>

// Overloaded ostream operator
std::ostream& operator<<( std::ostream& o, const CaesarText& c ) {
    o << "Original Text: " << c._originalText << "\n";
    o << "Shifted Text: " << c._shiftedText << "\n";
    return o;
}

// public friend function (visible in main) not actually a part of the class
// but performs operations on it.
// To perform the Caesar Shift here are 3 possible variations of implementing the same task.
void caesarShift( Caesar Text& text, int amount ) {
    // Bound amount to the number of characters in the alphabet 
    // the same value used in any of the three variations below.
    amount %= 26;

    // Older c++ style loop.
    /*for ( std::size_t i = 0; i < text._originalText.length(); i++ ) {
        char c = text._originalText[i] + amount;
        text._shiftedText += c;
    }*/

    // Modern C++ style loop
    /*for ( auto& c : text._originalText ) {
        text._shiftedText += c + amount;
    }*/

    // std::transform( s1.begin, s1.end, back_inserter( s2 ), lamda as predicate );
    /*std::transform( text._originalText.begin(), text._originalText.end(),
                std::back_inserter( text._shiftedText ),
                [amount]( unsigned char c ) -> unsigned char { return c + amount; }
    );*/    
}

至于执行Caesar Shift的3种不同变体，您可以取消注释相应的块部分。

如何根据用户输入c ++打开和读取文件

2 个答案: